Clutch-brake with permanent magnets



A. NYMAN May 27, 1969 CLUTCH-BRAKE WITH PERMANENT MAGNETS Sheet Filed June 13, 1967 INVENTOR ALEXANDER NYMAN BY ATTORNEY May 27, 1969 A. NYMAN CLUTCH-BRAKE WITH PERMANENT MAGNETS Filed June 13, 1967 United States Patent 3,446,321 CLUTCH-BRAKE WITH PERMANENT MAGNETS Alexander Nyman, Dover, Mass., assignor to Mohawk Data Sciences Corporation, East Herkimer, N.Y., a corporation of New York Filed June 13, 1967, Ser. No. 645,814 Int. Cl. F16d 11/06, 13/22, 67/02 US. Cl. 19218 Claims ABSTRACT OF THE DISCLOSURE assist means are provided to more positively control transfer of the output disk and stop lugs are provided to more accurately position it upon arrest.

Background of the invention This invention relates to bistable magnetic devices and, more particularly, to a clutch-brake for coupling intermittant motion in precise amounts to an output element.

Heretofore, magnetic clutch-brake systems have employed electromagnetic elements to couple either of two input members, one usually a constantly rotating shaft and the other usually a stationary member, to an output element, usually a rotatable shaft. This construction has been found somewhat lacking for several reasons, a principle one being the requirement for large amounts of electrical energy due to use of electromagnets. To minimize power consumption characteristics, great sacrifices must be made in switching speeds, torque transfer capacity and wear characteristics of the unit. Reduction of electrical power requirements means that lower magnetic fields are switched on and off at slower speeds, thus cutting down on the ulitmate torque available at the output and also lengthening the time required to transfer between the different states of the system. As a result of the longer transfer times, more slippage is allowed to take place between the coupling elements, with the result that greater wear is produced on the operating parts.

Objects and summary of the invention It is therefore an object of the invention to provide an improved magnetic clutch-brake having rapid transfer characteristics and high torque coupling capacity and reltively low electrical energy requirements.

In accordance with the principles of the invention, each input element is provided with a high-strength permanent magnetic field generated by an annular ceramic magnet equipped with a pair of annular, concentric pole pieces. A latching field continuously emanates from each set of pole pieces and acts on a magnetically-attractable shifting member movably connected to an output shaft. The shifting member is normally latched to one or the other of the sets of pole pieces and couples its movement (or nonmovement) to the output. To transfer output states, a degaussing coil located in the annular gap between the poles of the latched magnet is briefly pulsed with an electric current, causing the latching field to diminish and permitting the field emanating from the other set of pole pieces to attract the shifting member, thus coupling the output to the other input element. For applications calling for fixed-increment intermittant motion to be supplied to the output, additional mechanical assist means are provided to even more rapidly and positively eifect the transfer of the shifting member and to more accurately locate its stopping position when the output is transferring from a moving state to a non-moving state.

The only electrical energy required in the system of the invention is that need to pulse the degaussing coil at the time of transfer. Further, the non-degaussed magnetic field, being at its full strength at the instant transfer begins, causes a more rapid transfer of the shifting member from one set of latching poles to the other. This minimizes transfer slippage and extends the life of the operating parts.

These and other objects, features and advantages of the invention are explained in the following detailed description of a preferred embodiment thereof, the description being accompanied by drawings as follows.

Brief description of the drawings FIG. 1 is a side elevation view, partially cut away, showing one embodiment of a clutch-brake in accordance with the invention.

FIG. 2 is an exploded, perspective view of the clutchbrake of FIG. 1.

FIG. 3 is a side elevation view showing the details of one of the release-assist spring devices shown on the clutch side of the apparatus of FIG. 1.

Detailed description Referring to FIGS. 1, and 2, a preferred embodiment of the clutch-brake of the invention comprises an input shaft 2 journalled for rotation in a stationary frame 4 by bearing 6. An annular outer pole piece 8 having an annular pole face 9 is rigidly attached to shaft 2 as is an annular inner pole piece 10 having an annular pole face 11 concentric with pole face 9. Both of the pole pieces 8 and 10 are fabricated of a ferromagnetic material such as steel having a relatively high percentage of silicon to increase internal electrical resistance and minimize the possibility of eddy current building up during magnetic flux changes. To further minimize eddy currents, a pair of radial slots 13 and 16 are included in the pole pieces 8 and 10, respectively. Sandwiched between the pole pieces 8 and 10 is an annular permanent magnet 12. This magnet may be of the ceramic type, which is particularly well suited for use in the present invention. The general characteristics and advantages of this type of magnet are explained in some detail in copending patent application Ser. No. 639,590, filed May 9, 1967, and are not herein elaborated upon further. Such magnets are adapted to provide high flux densities for their weight and size when utilized with pole pieces configured so as to concentrate the field of the magnet in a small area. As is seen from FIG. 1, virtually all of the field of magnet 12 is directed between the annular gap defined between pole pieces 9 and 11. A suitable commercially available material for constructing this type of magnet is Indox V manufactured by the Indiana General Company.

Housed in the annular space 'between pole pieces 8 and 10' is a degaussing coil 14 which is electrically connected by a pair of lead wires 15 to a pair of concentric sliprings 57 and 59 supported on the outside face of pole piece 8. A pair of spring loaded contact brushes 61 and 63 electrically connect the sliprings 57 and 59, respectively, to a pair of lead wires 64 and 65 which are adapted to transmit a degaussing pulse, as described below, to coil 14 from a pulse generating circuit 101.

A stationary frame member 24 opposite frame 4 rotatably supports in bearing 26 an output shaft 22. This shaft has on its right-hand end a splined portion 38 of reduced diameter. A shift disk 20 is mounted via an internally splined hub 39 so as to be axially slidable on the splined portion 38 and at the same time rotatable with shaft 22 and angularly immovable with respect thereto. An end bolt 40 limits the rightward movement of disk 20 while the shoulder on shaft 22 limit its leftward movement.

A second magnetic unit comprising an annular ceramic permanent magnet 34 and a pair of annular pole pieces 28 and 30 is rigidly attached to frame 24 and mounted in alignment with the magnetic unit just described. Except for the fact that the magnetic unit 34, 28, 30 is stationary, it is virtually identical to the magnetic unit 12, 8, 10. The former unit is provided with a degaussing coil 42 located in the gap between pole faces 29 and 32 of the pole pieces 28 and 30. Coil 42 is electrically connected by a pair of lead Wires 44 to an external pulsing circuit 103 for supplying a degaussing pulse, as described below.

Operation Operation of the above-described clutch-brake system is as follows. In the condition shown in FIG. 1, constantly rotating input shaft 2 is connected to output shaft 22 by virtue of the fact that shifting disk 20 is latched across the pole faces 9-11 by the magnetic field emanating from magnet 12. At this time the permanent field of magnet 34 appears across the pole faces 29 and 32 and also interacts with disk 20 but has no significant influence thereon due to the latched condition of the disk and consequent very strong attraction thereof to the pole faces 9 and 11.

When it is desired to rapidly and accurately stop the rotation of output shaft 22 a pulse generated by circuit 101 is transmitted via lead wires 64 and 65, brushes 61 and 63, sliprings 57 and 59 and leads to coil 14 whereby a short duration magnetic field opposing the permanent field from magnet 12 is generated in the area of the pole faces 9-11 and temporarily nullified or severely diminishes the magnetic field thereacross. With its latching field gone, disk instantaneously is drawn under the influence of the field from magnet 34 into latching engagement with pole faces 2932, causing output shaft 22 to immediately cease rotation.

To resume rotation of shaft 22, a degaussing pulse from circuit 103 is applied to coil 42 via lead wires 44 and the latching field holding shifting disk 20 to the pole faces 29 and 32 is virtually instantaneously nullified, permitting the field from magnet 12 to draw the disk 20 into contact with rotating pole faces 9 and 11 whereby shaft 22 begins to rotate.

For application where the output shaft 22 must he stepped in fixed angular increments, mechanical assist means, as shown in FIGS. 1 and 3 may be provided to aid the magnetic fields in transferring and arresting the disk 20. A pair of spring-loaded rollers 47 are pivoted to the stationary frame 4 via pivot pin 52 (FIG. 3) journalled in fixed channel members 53. A compression spring 49 urges each roller 47 and support arm 50 counterclockwise about its pin 52 and a stop bolt 54 provides an adjustable limit to the counterclockwise freedom of arm 50. A pair of diametrically opposed ears 45 (also see FIG. 2) project from the periphery of disk 20 and each includes a leading edge stop surface 45a and a camming surface 451;. A pair of stop lugs 55, 180 degrees displaced about the periphery of disk 20, coact with the leading edges 45a under conditions described below to aid in arresting rotation of the disk.

When disk 20 is latched to poles 9 and 11 transmitting rotation to shaft 22, each half revolution of the disk the camming portion 45b of each ear 45 contacts a roller 47 and simultaneously thereto a release pulse is applied to coil 14 by circuit 101. The combined influence of the field of magnet 34 and the camming of the portions 45b of ears 45 on the rollers 47 rapidly forces disk 20 into latching contact with poles 29 and 32 of magnet 34. Just as this contact is made, the leading edges 45a of ears 45 engage the fixed stop lugs 55 attached to frame member 24. This ensures that disk 20 is arrested in precise increments and in the most. rapid time possible, minimizing wear due to slippage.

Of course, if shaft 22 is to be stepped in angular increments other than 180, the number of ears 45 provided on disk 20 and the number and location of stop lugs 55 must be altered appropriately.

To assist disk 20 in its release from poles 29, 32 when output rotation is to be resumed, a dish-shaped spring 36, known sometimes as a Belleville" spring, is provided between the face of pole piece 30 and the disk 20. This spring is constructed such that its resistance to leftward movement of disk 20 is slight when the disk is starting its travel from poles 9, 11 to poles 29, 32 and increases as the disk approaches nearer the stationary poles. This enable the spring 36 to provide a maximum assist to disk 20 when it is travelling from left to right (the spring force being most effective when the attracting force of magnet 12 is lowest) while causing a minimum delay in the right to left transfer of the disk.

Of course, it is apparent that the input magnetic units 28, 30, 34 and 8, 10, 12 need not necessarily be stationary and rotatable, respectively, as described above. For example both could be rotating in the same or opposite directions. Further, their velocities need not necessarily be constant but may be variable, as suits the requirements of the particular application.

T o recapitulate, it is seen that the clutch-brake system of the invention operates with a minimum requirement for electrical energy due to the fact that the latching forces are generated by permanent magnets. Also, the full strength magnetic field in existence at the poles 29, 32 and 9, 11 at the instant the opposite magnetic unit is unlatched causes rapid transfer of disk 20 under magnetic attraction and in the situations calling for intermittent rotation of shaft 22 in fixed angular increments the assisting springs 49 and 36 together with stop lugs 55 result in extremely rapid, positive and accurate stepping control of shaft 22.

While the invention has been disclosed with reference to a preferred embodiment thereof, it is to be understood that numerous modifications and variations additional to those suggested may be made therein without departing from the true spirit and scope of the invention.

I claim:

1. A dynamic multistable device comprising, in combination:

a magnetically-attractable output member;

a plurality of input members, each comprising means for providing a fixed magnetic field to attract the output member into physical coaction with the input member, and each comprising means for providing a selectively-actuatable temporary magnetic field in counteraction to the fixed magnetic field to overcome its attraction of the output member, said input members being arranged with respect to said output member to provide instantaneous coaction between one input member and the output member;

means for mechanically driving at least one input member; and

means for alternately actuating the temporary magnetic field means to provide alternate coaction of the input means with the output means.

2. The device described in claim 1, wherein the output means is a rotatable disk that is mounted for displacement along its axis of rotation between two input members, one of which is adapted for frictional coaction with one surface of the disk and the other of which is adapted for frictional coaction with the other surface of the disk.

3. The device described in claim 1, wherein one input member is rigidly mounted and, when coacting with the output member, inhibits its motion.

4. The device described in claim 2, wherein one input member is rigidly mounted and, when coacting with the output member, inhibits its motion.

5. The device described in claim 2, wherein the output member is mounted on a splined rotatable shaft.

6. A dynamic bistable mechanism comprising in combination:

an output shaft;

a magnetically-attractable, disk-shaped output member mounted on the output shaft with rotational rigidity and axial displaceability;

two input members, one stationarily and one rotatably mounted, each comprising:

a disk-shaped permanent magnet,

two magnetizable, disk-shaped pole pieces, one arranged on each side of the magnet, where the edges of the pole pieces are raised to form annular pole pieces of different diameter in the same plane, and

a demagnetizing coil mounted between the ring-shaped raised edges;

the input members arranged with the raised edges of the respective pole pieces on opposite sides of the output member and displaced by a distance slightly greater than the thickness of the output member to permit frictional coaction between the raised pole pieces of either input member with the output member;

means for driving the rotatable mounted input memher; and

means for alternately actuating the demagnetizing coils;

whereby the output member is alternately driven and stopped as it is displaced along its axis for alternate caction with the raised pole pieces of the driven and stationary input members, the axial position of the output member being displaced from that input member whose demagnetizing coil is most recently actuated.

7. The mechanism set forth in claim 6, further comprising:

a camming element fixed to said output member;

a stationary camming roller positioned to engage said camming element once per revolution of said output member when the latter is frictionally coacting with said rotatable input member, said engagement causing a camming force to be exerted on said output member parallel to its axis and in a direction away from said rotatable input member; and

means for actuating the demagnetizing coil of said rotatable input member substantially simultaneously with each engagement of said camming element and camming roller.

8. The mechanism set forth in claim 7, further comprising:

a fixed stop lug positioned to engage a surface of said camming element when said output member is frictionally coacting with said stationary input member; and

a release spring urging said output member in a direction away from said stationary input member.

9. A magnetic clutch-brake, comprising, in combination:

a pair of magnetic input members rotatable about an axis with respect to one another and spaced from one another along said axis, at least one of said input members including an annular permanent ceramic magnet connected to a pair of pole pieces having annular, concentric pole faces with a selectively energizable demagnetizing coil mounted between said pole pieces; and

a rotatable, axially transferable output member mounted between said input members, said output member being adapted to be magnetically latched to said one of said input members, assuming the rotational state thereof, and to be drawn into magnetic engagement with the other of said input members upon energization of said demagnetizing coil whereby said output member assumes the rotational state of said other input member.

10. The magnetic clutch-brake set forth in claim 9 wherein said other of said input members also includes an annular permanent ceramic magnet connected to a pair of pole pieces having annular, concentric pole faces with a demagnetizing coil mounted between said pole pieces.

References Cited UNITED STATES PATENTS 2,646,145 7/1953 Durston 192-182 2,738,449 3/ 1956 Mason.

2,823,776 2/ 1958 Pierce 19218.2 2,848,085 8/1958 Mannaioni 192-18.2 X 2,886,149 5/1959 Baermann 192-18.2 2,915,160 12/1959 Schneider 19233 X OTHER REFERENCES IBM Technical Disclosure Bulletin, Magnetic Print Wheel Clutch, by P. Gmeiner, vol. 4, N0. 1, June 1961, pp. 8-9.

BENJAMIN W. WYCHE HI, Primary Examiner.

US. Cl. X.R. 19233, 48.2, 84; 335-229 

